CampTix: Issues with the [camptix_attendees] shortcode

[coreymckrill]

Coming out of a Slack discussion in #meta-wordcamp, this issue is to collect various problems with [camptix_attendees] from Meta Trac (meta-2282, meta-2413) and elsewhere.

Some problems are:

• For larger WordCamps (200+), having all of the attendees on the page at once is unwieldy, and it is not easy to browse or find specific people.
• The columns parameter for the shortcode is buggy, and doesn't work correctly in some situations such as when there are less attendees than there are columns.
• Lazy loading the attendee gravatars improves performance, but it may be using an outdated approach, given that a native solution may be coming to WP Core in 5.4.
• The HTML markup and CSS to output the columns is not using a modern approach (floated divs instead of flexbox or css-grid).

One proposed solution is to render the attendees list via JS instead of PHP, which would make it easier to add dynamic filtering/searching. On the back end, we could also convert the shortcode into a block, which would improve the UX for configuring options and make it more self-documenting (and anyway, ideally all of WordCamp's shortcodes will eventually become blocks).

[timiwahalahti]

Related from Trac: #2940 WordCamp Attendee JSON

[ryelle]

meta-3217 is another we could add to this batch, to allow organizers to assign a default gravatar image (the potential attendee block could have an image upload attached).